Multilayer capacitor

ABSTRACT

A multilayer capacitor includes a body, a plurality of internal electrodes and external electrodes disposed on external surfaces of the body and electrically connected to the internal electrodes, wherein in the body, corners of cover portions include curved surfaces, and 10 μm≤R≤T/4 in which R is a radius of curvature of the curved surface corners and T is a thickness of the body, and when a distance from a surface of the body to an internal electrode closest to the surface of the body among the plurality of internal electrodes is a margin, a margin (δ) of each of the corners formed as the curved surfaces in the cover portions is greater than or equal to a margin (Wg) of the body in a width direction.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application claims the benefit of priority to Korean PatentApplications No. 10-2018-0102001 filed on Aug. 29, 2018 and No.10-2018-0123342 filed on Oct. 16, 2018 in the Korean IntellectualProperty Office, the entire disclosures of which are incorporated hereinby reference.

TECHNICAL FIELD

The present disclosure relates to a multilayer capacitor.

BACKGROUND

A capacitor is an element that may store electricity therein, and when avoltage is applied to the capacitor in a state in which two electrodesare basically disposed to face each other, electricity is accumulated inthe respective electrodes. When a direct current (DC) voltage is appliedto the capacitor, a current flows in the capacitor while the electricityis accumulated, but when the accumulation of the electricity iscompleted, the current does not flow in the capacitor. Meanwhile, whenan alternating current (AC) voltage is applied to the capacitor, an ACcurrent flows in the capacitor while polarities of the electrodes arealternated.

Such a capacitor may be divided into several kinds of capacitors such asan aluminum electrolytic capacitor in which electrodes are formed ofaluminum and a thin oxide layer is disposed between the electrodesformed of aluminum, a tantalum capacitor in which tantalum is used as anelectrode material, a ceramic capacitor in which a dielectric materialhaving a high dielectric constant such as a barium titanate is usedbetween electrodes, a multilayer ceramic capacitor (MLCC) in whichceramic having a high dielectric constant is used in a multilayerstructure as a dielectric material provided between electrodes, a filmcapacitor in which a polystyrene film is used as a dielectric materialprovided between electrodes, and the like, depending on a kind ofinsulator provided between electrodes.

Among them, the multilayer ceramic capacitor has been recently usedmainly in various fields such as a high frequency circuit, and the like,since it has excellent temperature characteristics and frequencycharacteristics and may be implemented at a small size.

Amultilayer ceramic capacitor according to the related art includes alaminate formed by stacking a plurality of dielectric sheets andexternal electrodes disposed on external surfaces of the laminate andhaving different polarities, wherein internal electrodes alternatelystacked in the laminate may be electrically connected to the respectiveexternal electrodes.

Recently, in accordance with miniaturization and an increase in a degreeof integration of an electronic product, many studies on miniaturizationand an increase in a degree of integration of the multilayer ceramiccapacitor have been conducted. Particularly, in the multilayer ceramiccapacitor, various attempts to increase the number of stacked dielectriclayers and improve connectivity of internal electrodes by decreasingthicknesses of the dielectric layers in order to increase a capacitanceof the multilayer ceramic capacitor and miniaturize the multilayerceramic capacitor have been conducted.

Particularly, in developing a multilayer ceramic capacitor having anultrahigh capacitance, it has become more important to securereliability of a product in which the numbers of stacked thin filmdielectric layers and internal electrodes are many. As the numbers ofstacked dielectric layers and internal electrodes are increased, stepsdue to thickness differences between the internal electrodes and thedielectric layers are increased. These steps cause warpage phenomena ofdistal end portions of the internal electrodes due to stretching of thedielectric layers in a transversal direction in a densifying process ofcompressing a body.

That is, the distal end portions of the internal electrodes are bent inorder to fill the steps, and in margin portions, empty spaces due to thesteps are removed by depression of covers and a reduction in a marginwidth. The empty spaces due to the steps are removed, such thatcapacitance layers are also stretched by the reduced margin width.Reliability of the multilayer ceramic capacitor such as withstandvoltage characteristics or the like is reduced due to structuralirregular stretching of the internal electrodes as described above.

In order to solve such a problem, a method of cutting opposite endsurfaces of the body in a length direction and then attaching endsurface margin portions to the opposite end surfaces has been developed.However, such a method may be complicated, such that productivity may below, and when the end surface margin portions are formed to have a smallthickness, a thickness of corner margin portions also becomes small,such that moisture resistance reliability of the body is deteriorated.

SUMMARY

An aspect of the present disclosure may provide a multilayer capacitorin which an effective volume may be significantly increased and moistureresistance reliability may be secured.

According to an aspect of the present disclosure, a multilayer capacitormay include a body including a stacked structure of a plurality ofdielectric layers and a plurality of internal electrodes stacked witheach of the plurality of dielectric layers interposed therebetween; andexternal electrodes disposed on external surfaces of the body andelectrically connected to the plurality of internal electrodes, whereinthe body includes an active portion forming a capacitance by theplurality of internal electrodes disposed therein and cover portionsdisposed on upper and lower surfaces of the active portion,respectively, in a stacking direction of the plurality of dielectriclayers, the body has a first surface and a second surface, to which theplurality of internal electrodes are exposed, opposing each other, athird surface and a fourth surface which oppose each other in thestacking direction, and a fifth surface and a sixth surface which areconnected to the first to fourth surfaces and oppose each other. In thebody, corners of the cover portions may include curved surfaces, and 10μm≤R≤T/4 in which R is a radius of curvature of the curved surfaces andT is a thickness of the body in the stacking direction. A margin (δ) ofeach of the corners of the cover portions is greater than or equal to amargin (Wg) of side portions of the body, where the margin (δ) is adistance from a surface of the corners of the cover portions to aclosest portion of the plurality of internal electrodes, and the margin(Wg) is a distance from the fifth or sixth surface of the body to aclosest portion of the plurality of internal electrodes.

In the cover portions, corners at which the third surface is connectedto the fifth surface and the sixth surface and corners at which thefourth surface is connected to the fifth surface and the sixth surfacemay include curved surfaces.

1≤δ/Wg≤1.2.

0.5 μm≤Wg≤T/12.

0.5 μm≤Wg≤15 μm.

Wg<Tg in which Tg is a margin of each of the third surface and thefourth surface.

10 μm≤R≤60 μm in which R is the radius of curvature.

The margin (δ) of each of the corners formed as the curved surfaces inthe cover portions may be smaller than the radius (R) of curvature.

The plurality of internal electrodes may have a uniform width.

In the body, when outer regions surrounding the plurality of internalelectrodes are margin regions, a density of the dielectric layer may belower in the margin regions than in the other regions.

According to another aspect of the present disclosure, a multilayercapacitor may include a body including a stacked structure of aplurality of dielectric layers and a plurality of internal electrodesstacked with each of the plurality of dielectric layers interposedtherebetween; and external electrodes disposed on external surfaces ofthe body and electrically connected to the plurality of internalelectrodes, wherein the body includes an active portion forming acapacitance by the plurality of internal electrodes disposed therein andcover portions disposed on upper and lower surfaces of the activeportion, respectively, in a stacking direction of the plurality ofdielectric layers, the body has a first surface and a second surface, towhich the plurality of internal electrodes are exposed, opposing eachother, a third surface and a fourth surface which oppose each other inthe stacking direction, and a fifth surface and a sixth surface whichare connected to the first to fourth surfaces and oppose each other. Inthe body, corners of the cover portions include curved surfaces. Amargin (δ) of each of the corners of the cover portions is greater thanor equal to a margin (Wg) of side portions of the body, where the margin(δ) is a distance from a surface of the corners of the cover portions toa closest portion of the plurality of internal electrodes, and themargin (Wg) is a distance from the fifth or sixth surface of the body toa closest portion of the plurality of internal electrodes. In the body,when an outer region surrounding the plurality of internal electrodes isa margin region, a density of a dielectric layer in the margin region islower than a density of a dielectric layer in other regions.

In the margin region, the plurality of dielectric layers may include atleast two layers having different densities, and a density of adielectric layer adjacent to the plurality of internal electrodes may behigher than a density of another dielectric layer of the at least twolayers.

The margin region may include a plurality of pores.

The plurality of pores may be needle-like pores.

The plurality of pores may have a form in which they are aligned in ashape corresponding to an outer shape of the body.

The plurality of pores may be composed of a plurality of rows, whereeach row is defined as a row of pores that are aligned in the shapecorresponding to the outer shape of the body.

Pore densities of the plurality of rows may be different from oneanother, and a pore density of a region closer to an outer surface ofthe body may be lower than densities of other regions in the pluralityof rows.

BRIEF DESCRIPTION OF DRAWINGS

The above and other aspects, features, and advantages of the presentdisclosure will be more clearly understood from the following detaileddescription taken in conjunction with the accompanying drawings, inwhich:

FIG. 1 is a schematic perspective view illustrating a multilayercapacitor according to an exemplary embodiment of the presentdisclosure;

FIGS. 2 and 4 are cross-sectional views taken along line I-I′ of themultilayer capacitor of FIG. 1, and in FIG. 4, an outer side of a regionin which internal electrodes are disposed is denoted by dotted lines;

FIG. 3 is a cross-sectional view taken along line II-II′ of themultilayer capacitor of FIG. 1; and FIGS. 5 through 13 are viewsillustrating manufacturing processes of a multilayer capacitor accordingto an exemplary embodiment of the present disclosure.

DETAILED DESCRIPTION

Hereinafter, exemplary embodiments of the present disclosure will now bedescribed in detail with reference to the accompanying drawings.

FIG. 1 is a schematic perspective view illustrating a multilayercapacitor according to an exemplary embodiment of the presentdisclosure. FIGS. 2 and 4 are cross-sectional views taken along lineI-I′ of the multilayer capacitor of FIG. 1, and in FIG. 4, an outer sideof a region in which internal electrodes are disposed is denoted bydotted lines. FIG. 3 is a cross-sectional view taken along line II-II′of the multilayer capacitor of FIG. 1.

Referring to FIGS. 1 through 4, a multilayer capacitor 100 according toan exemplary embodiment of the present disclosure may include a body 110including dielectric layers 111 and a plurality of internal electrodes121 and 122 stacked with each of the dielectric layers 111 interposedtherebetween, and external electrodes 131 and 132. In the body 110,corners of cover portions A 1 and A2 may be curved surfaces. In thiscase, as described below, 10 μm≤R≤T/4 in which R is a radius ofcurvature of the curved surface corners of the cover portions A1 and A2in the body 110 and T is a thickness of the body 110.

The body 110 may have a form in which a plurality of dielectric layers111 are stacked, and may be obtained by stacking and then sintering, forexample, a plurality of green sheets. The plurality of dielectric layers111 may have a form in which they are integrated with one another bysuch a sintering process. A shape and a dimension of the body 110 andthe number of stacked dielectric layer 111 are limited to thoseillustrated in the present exemplary embodiment, and the body 110 mayhave a shape similar to a rectangular parallelepiped shape, for example,as illustrated in FIG. 11. The body 110 may have a first surface S1 anda second surface S2 to which the internal electrodes 121 and 122 areexposed, respectively, a third surface S3 and a fourth surface S4opposing each other in a stacking direction (Z direction) of theplurality of dielectric layers 111, and a fifth surface S5 and a sixthsurface S6 connected to the first to fourth surfaces S1, S2, S3, and S4and opposing each other.

The dielectric layer 111 included in the body 110 may include a ceramicmaterial having a high dielectric constant, for example, a BT-basedceramic material, that is, barium titanate (BaTiO₃)-based ceramicmaterial, but may include another material known in the related art aslong as a sufficient capacitance may be obtained. The dielectric layer111 may further include an additive, an organic solvent, a plasticizer,a binder, a dispersant, and the like, if necessary, together with theceramic material, which is a main component. Here, the additives mayinclude a metal component, and may be added in a metal oxide form in amanufacturing process. An example of such a metal oxide additive mayinclude at least one of MnO₂, Dy₂O₃, BaO, MgO, Al₂O₃, SiO₂, Cr₂O₃, andCaCO₃.

Each of the plurality of internal electrodes 121 and 122 may be obtainedby printing and then sintering a paste including a conductive metal at apredetermined thickness on one surface of the ceramic green sheet. Inthis case, the plurality of internal electrodes 121 and 122 may includefirst and second internal electrodes 121 and 122 exposed, respectively,to the first surface S1 and the second surface S2 of the body 110opposing each other, as illustrated in FIG. 3. In this case, the firstand second internal electrodes 121 and 122 may be connected to differentexternal electrodes 131 and 132, respectively, to have differentpolarities when the multilayer capacitor is driven, and may beelectrically separated from each other by each of the dielectric layers111 disposed therebetween. As in an illustrated form, the plurality ofinternal electrodes 121 and 122 may have a uniform width. However,according to another exemplary embodiment, the number of externalelectrodes 131 and 132 and a connection manner of the internalelectrodes 121 and 122 may be changed. A main material of the internalelectrodes 121 and 122 may include, for example, nickel (Ni), copper(Cu), palladium (Pd), silver (Ag), or the like, or alloys thereof.

The external electrodes 131 and 132 may include first and secondexternal electrodes 131 and 132 disposed on external surfaces of thebody 110 and electrically connected, respectively, to the first andsecond internal electrodes 121 and 122. The external electrodes 131 and132 may be formed by a method of manufacturing a material including aconductive metal in a form of a paste and then applying the paste to thebody 110, and the conductive metal may include, for example, nickel(Ni), copper (Cu), palladium (Pd), gold (Au), or alloys thereof. Inaddition, the external electrodes 131 and 132 may further includeplating layers, if necessary, in order to mount the multilayer capacitor100 on a board.

In the present exemplary embodiment, corners of the body 110 may includecurved surfaces to suppress a chipping defect. In addition, structuralcharacteristics of the body 110 according to the present exemplaryembodiment can be detailed as follows. Specifically, when a distancefrom a surface of the body 110 to an internal electrode closest to thesurface of the body 110 among the plurality of internal electrodes 121and 122 is defined as a margin, a margin of each of the corners formedas the curved surfaces in the cover portions A1 and A2 may be greaterthan or equal to a margin of the body 110 in a width direction, whichwill be described below.

In the present exemplary embodiment, a size of the margin, a radius ofcurvature of the curved surface, a thickness, a length, and the like, inthe body 110 may be determined based on a desired performance of themultilayer capacitor. The multilayer capacitor 100 according toexemplary embodiments of the present disclosure may have a high level ofcapacitance in spite of being miniaturized, and furthermore, may have animproved moisture resistance reliability. This will hereinafter bedescribed in detail.

The body 110 may be divided into an active portion A3 and the coverportions A1 and A2. Here, the active portion A3 may correspond to aregion forming a capacitance by the plurality of internal electrodes 121and 122 disposed therein. The cover portions A1 and A2 may be disposedon upper and lower surfaces of the active portion A3, respectively, inthe stacking direction (the Z direction in the drawings) of theplurality of dielectric layers 111.

As described above, in the cover portions A1 and A2 of the body 110, thecorners may include the curved surfaces, which may serve to reduce thechipping defect of the multilayer capacitor 100. In detail, in the coverportions A1 and A2, corners (upper curved surface corners in FIG. 2) atwhich the third surface S3 is connected to the fifth surface S5 and thesixth surface S6 and corners (lower curved surface corners in FIG. 2) atwhich the fourth surface S4 is connected to the fifth surface S5 and thesixth surface S6 may include curved surfaces.

Optimal conditions of the size of the margin and the radius ofcurvature, the thickness, the length, and the like, of the curvedsurface in the body 110 will be described with reference to FIG. 4. InFIG. 4, a region in which the internal electrodes 121 and 122 aredisposed is defined as an internal electrode region 120 and is denotedby dotted lines. In this case, a Z direction refers to a thicknessdirection of the body 110, a Y direction refers to a width direction ofthe body 110, and T and W refer to a thickness and a width of the body110, respectively.

First, a margin of the body 110 may refer to a distance from the surfaceof the body 110 to the internal electrode closest to the surface of thebody 110 among the plurality of internal electrodes. In detail, a marginof each of the corners formed as the curved surfaces in the coverportions A1 and A2 may be δ. In addition, a margin of each of the fifthsurface S5 and the sixth surface S6 may be Wg, which corresponds to amargin of the body 110 in the width direction. In the present exemplaryembodiment, the margin δ of the curved surface corner may be greaterthan or equal to the margin Wg of the body 110 in the width direction.In the related art, the internal electrodes were not aligned with eachother, such that it was difficult to form the margin of the body in thewidth direction. In order to solve such a problem, a process ofseparately forming the margin of the body in the width direction wasused. In such a structure, it is difficult to sufficiently secure themargin δ of the curved surface corner of the body 110, and particularlyin a case in which the body 110 is miniaturized and the number ofstacked internal electrodes is increased, moisture resistancereliability of the body 110 is deteriorated.

In the present exemplary embodiment, as described below, the corners ofthe body 110, more specifically, the corners of the cover portions A1and A2 may include the curved surfaces by a process of spraying aceramic paste. Due to such a form, the margin δ of the curved surfacecorner may be sufficiently secured, and may be greater than or equal tothe margin Wg of the body 110 in the width direction. In more detail,1≤δ/Wg≤1.2 in which δ is the margin of the curved surface corner and Wgis the margin of the body 110 in the width direction. When the margin δof the curved surface corner exceeds 1.2 times the margin Wg of the body110 in the width direction, widths of the internal electrodes 121 and122 in the cover portions A1 and A2 may be significantly reduced. Assuch a capacitance may be reduced.

As the margin δ of the curved surface corner is increased, the moistureresistance reliability may be improved even in the miniaturized body110, and the body 110 may include a number of internal electrodes 121and 122 to implement an improved capacitance. This means an increase inthe capacitance, that is, an effective volume, when calculated on thebasis of the same volume of the body 110.

Meanwhile, in the present exemplary embodiment, the internal electrodes121 and 122 disposed in the active portion A3 may have a uniform width.The uniform width of the internal electrodes 121 and 122 may be achievedby a process of dicing a ceramic laminate in individual chip units, asdescribed below. Here, uniformity of the width of the internalelectrodes 121 and 122 may be determined on the basis of positions ofend portions of the internal electrodes 121 and 122, and a deviation ofthe positions of the end portions of the internal electrodes 121 and 122in the width direction (the Y direction) may be smaller than or equal to0.1 μm.

In addition, Wg<Tg in which Tg is a margin of the body 110 in thethickness direction, that is, a margin of each of the third surface S3and the fourth surface S4, and Wg is the margin of the body 110 in thewidth direction. As described below, the margin Tg of the body 110 inthe thickness direction and the margin Wg of the body 110 in the widthdirection may be formed by the same process. When dielectric layerscorresponding to base layers 116 and 117 for covers are disposed on theuppermost and lowermost internal electrodes 121 and 122, respectively,the margin Tg of the body 110 in the thickness direction may be slightlygreater than the margin Wg of the body 110 in the width direction. Inaddition, 0.5 μm≤Wg≤15 μm in which Wg is the margin of the body 110 inthe width direction, and the margin Wg of the body 110 in the widthdirection may be designed in order to secure the moisture resistancereliability of the body 110 and secure a sufficient capacitance.Likewise, 0.5 μm≤Tg≤15 μm in which Tg is the margin of the body 110 inthe thickness direction. In addition, the margin Wg of the body 110 inthe width direction may be set in consideration of the thickness T ofthe body 110, and specifically, 0.5 μm≤Wg≤T/12. Here, the thickness T ofthe body 110 may be, for example, about 200 to 400 μm.

In addition, the radius R of curvature of each of the corners formed asthe curved surfaces in the cover portions A1 and A2 may be designed toendure a weight of the multilayer capacitor 100 and chipping due to aload in a process, and specifically, the radius R of curvature is in arange of 10 μm≤R≤60 μm. In another exemplary embodiment of the presentdisclosure, the radius R of curvature may be set in consideration of thethickness T of the body 110, and specifically, is in a range of 10μm≤R≤T/4. As described above, the thickness T of the body 110 may be,for example, about 200 to 400 μm. In addition, as illustrated in FIG. 4,in the curved surface corners of the cover portions A1 and A2, themargin δ may be smaller than the radius R of curvature.

Meanwhile, in the body 110, when outer regions surrounding the pluralityof internal electrodes 121 and 122, that is, regions surrounding theinternal electrode region 120 in FIG. 4 are margin regions 112 and 113,a density of the dielectric layer 111 may be lower in the margin regions112 and 113 than in the other regions. As described below, the marginregions 112 and 113 may be obtained in a manner of manufacturing andthen coating a ceramic laminate, and a difference in the density may bedue to a difference in such a manufacturing manner. Here, the densitymay be understood as a concept that is inversely proportional to adensity of pores existing in the dielectric layer.

An example of a method of manufacturing the multilayer capacitor will bedescribed with reference to FIGS. 5 through 13 in order to more clearlyunderstand the structure of the multilayer capacitor described above.

First, as illustrated in FIG. 5 according to an exemplary embodiment ofthe present disclosure, a ceramic laminate 115 may be prepared bystacking the dielectric layers 111 and the internal electrodes 121 and122. Here, since the dielectric layer 111 is in a state before beingsintered, the dielectric layer 111 may be in a state of a ceramic greensheet. The ceramic green sheet may be manufactured by mixing ceramicpowders, a binder, a solvent, and the like, with one another to prepareslurry and manufacturing the slurry in a sheet shape having a thicknessof several micrometers by a doctor blade method. Then, the ceramic greensheet may be sintered to form the dielectric layer 111.

A conductive paste for an internal electrode may be applied onto theceramic green sheet to form an internal electrode pattern on the ceramicgreen sheet. In this case, the internal electrode pattern may be formedby a screen printing method or a gravure printing method. The conductivepaste for an internal electrode may include a conductive metal and anadditive. The additive may be one or more of a non-metal and a metaloxide. The conductive metal may include nickel. The additive may includebarium titanate or strontium titanate as the metal oxide.

A plurality of ceramic green sheets on which the internal electrodepatterns are formed may be stacked and pressed to implement the ceramiclaminate 115. In this case, the ceramic laminate 115 may include thebase layers 116 and 117 for covers disposed at the uppermost portion andthe lowermost portion thereof to effectively protect the internalelectrodes 121 and 122. In this case, the base layers 116 and 117 forcovers may include the same material as that of the dielectric layer 111or a material different from that of the dielectric layer 111 dependingon an intended function, and may be thicker than the dielectric layer111. Then, the ceramic laminate 115 may be diced in individual chipunits, if necessary. In this case, the internal electrodes 121 and 122may be exposed in order to be connected to the external electrodes 131and 132. The internal electrodes 121 and 122 exposed by a dicing processmay have a uniform width. For example, a difference between the largestwidth and the smallest width of the internal electrodes 121 and 122 maybe less than 0.1 μm.

Then, coating layers 118 (see FIG. 10) may be disposed on surfaces ofthe ceramic laminate 115. To this end, an appropriate coating processmay be performed. In the present exemplary embodiment, as illustrated inFIG. 6, a method of spray-coating a ceramic slurry 202 using a sprayapparatus 201 may be used. In this case, the ceramic slurry 202 mayfurther include the same component as that of the ceramic green sheetfor forming the dielectric layer 111 or a component giving fluidity tothe ceramic green sheet, for example, a liquid binder, or the like. Anexample of the present coating process will be described. First, asillustrated in FIGS. 7 and 8, the ceramic laminates 115 may be disposedin a coating apparatus 301, and air currents (denoted by arrows in FIGS.7 and 8) may be generated from the bottom of the coating apparatus 301toward the top thereof. After the ceramic laminate 115 is floated inthis manner, the ceramic slurry 202 may be sprayed to the ceramiclaminate 115 through a nozzle of the spray apparatus 201 disposed on thebottom (see FIG. 7) or the top (see FIG. 8) of the coating apparatus301. Unlike the forms illustrated in FIGS. 7 and 8, the sprayingapparatus 201 may also be disposed on a side portion of the coatingapparatus 301. The coating layers 118 having a uniform thickness may bedisposed on the surfaces of the ceramic laminates 115 in such a coatingmanner. The coating layers 118 are separately formed after the ceramiclaminate 115 is manufactured, such that a margin region of the body 110may be uniformly and thinly formed, and a margin having a sufficientthickness in a corner region of the body 110 having a poor moistureresistance performance may be obtained.

In addition, as another coating manner, as illustrated in FIG. 9, acoating apparatus 302 having a spherical container form may be used. Inthis case, protrusions 303 may be disposed on an inner side of thecoating apparatus 302. The ceramic laminate 115 may be overturned andmoved while the coating apparatus 302 is rotated. In this process, theceramic laminate 115 may be uniformly coated.

FIG. 10 is a view illustrating a state in which the coating layers 118are disposed on all the surfaces of the ceramic laminate 115, and FIG.11 is a cross-sectional view taken along line III-III′ of FIG. 10. Asillustrated in FIGS. 10 and 11, when the ceramic laminate 115 issubjected to the coating process described above, corners of the coatinglayers 118 may have curved surfaces. Then, the ceramic laminate 115 maybe sintered in a state in which the coating layers 118 are applied.Therefore, the ceramic green sheets included in the ceramic laminate 115and the coating layers 118 may become an integral body.

After a sintering process, parts of the body 110 may be removed toexpose the internal electrodes 121 and 122. Here, surfaces of the body110 on which the internal electrodes 121 and 122 are exposed maycorrespond to the first surface S1 and the second surface S2 describedwith reference to FIG. 1. However, other surfaces of the body 110 mayalso be exposed, if necessary. As a surface polishing process ofremoving parts of the body 110, a polishing process, a grinding process,or the like, may be used. FIG. 12 illustrates the body 110 subjected tothe surface polishing process after the sintering process and theinternal electrodes 121 and 121 exposed from the body 110. Then, theexternal electrodes may be disposed to be connected to the exposedinternal electrodes 121 and 122.

Meanwhile, in the process described above, the dielectric layer 111 maybe formed of the ceramic green sheet, and margin regions, accurately,regions except for the base layers 116 and 117 for covers in the marginregions may be formed by a coating process by the spraying of theceramic slurry. Therefore, there may be a difference in an internalstructure of the body 110 after the sintering process. In other words,characteristics such as a density or the like may be different betweenthe internal electrode region 120 and the margin regions 112 and 113 ofthe body 110. This will be described with reference to FIG. 13. FIG. 13is an enlarged plan view illustrating region A of FIG. 12.

When comparing a density of the dielectric layer 111 between the marginregions and a region (that is, the internal electrode region) other thanthe margin regions in the body 110, the density may be relatively lowerin the margin regions 112 and 113 than in the region other than themargin regions. In addition, in the margin regions 112 and 113, adensity may be relatively higher in a region close to the internalelectrodes 121 and 122 than in a region close to an outer portion of thebody 110. In other words, in the margin regions 112 and 113, thedielectric layers 111 may be at least two layers having differentdensities, and a density of the dielectric layer 111 may be higher in alayer, adjacent to the plurality of internal electrodes 121 and 122, ofthe at least two layers. In this case, regions corresponding to the baselayers 116 and 117 for covers before the sintering process are formed bystacking the ceramic green sheets, and may thus have a density higherthan that of the other regions of the margin regions 112 and 113.

These density characteristics of the margin regions 112 and 113 may beobtained by the coating process described above. When the ceramic slurryis sprayed, several-fold thin coating layers may be formed on thesurfaces of the ceramic laminate 115, and a plurality of pores may beformed between the coating layers and may remain even after thesintering process. As illustrated in FIG. 13, a plurality of needle-likepores P may remain in the margin regions 112 and 113 of the body 110.Since the plurality of needle-like pores P are generated in a process offorming the several-fold thin coating layers, a plurality of rows R1,R2, and R3 formed by the plurality of needle-like pores P may have aform in which they are aligned in a shape corresponding to an outershape of the body 110. Pore densities of the plurality of rows R1, R2,and R3 by the plurality of needle-like pores P may be different from oneanother, and as a region becomes closer to the surface of the body 110,the region may be later coated, and a pore density of the region maythus be relatively lower.

As set forth above, the multilayer capacitor according to the exemplaryembodiment of the present disclosure may be advantageous in terms ofminiaturization, may have a high capacitance, and may have excellentmoisture resistance characteristics to have a high reliability.

While exemplary embodiments have been shown and described above, it willbe apparent to those skilled in the art that modifications andvariations could be made without departing from the scope of the presentinvention as defined by the appended claims.

What is claimed is:
 1. A multilayer capacitor comprising: a bodyincluding a stacked structure of a plurality of dielectric layers and aplurality of internal electrodes stacked with each of the plurality ofdielectric layers interposed therebetween; and external electrodesdisposed on external surfaces of the body and electrically connected tothe plurality of internal electrodes, wherein the body includes anactive portion forming a capacitance by the plurality of internalelectrodes disposed therein and cover portions disposed on upper andlower surfaces of the active portion, respectively, in a stackingdirection of the plurality of dielectric layers, the body has a firstsurface and a second surface, to which the plurality of internalelectrodes are exposed, opposing each other, a third surface and afourth surface which oppose each other in the stacking direction, and afifth surface and a sixth surface which are connected to the first tofourth surfaces and oppose each other, in the body, corners of the coverportions include curved surfaces, and a margin (δ) of each of thecorners of the cover portions is greater than or equal to a margin (Wg)of side portions of the body, where the margin (δ) is a distance from asurface of the corners of the cover portions to a closest portion of theplurality of internal electrodes, and the margin (Wg) is a distance fromthe fifth or sixth surface of the body to a closest portion of theplurality of internal electrodes.
 2. The multilayer capacitor of claim1, wherein 10 μm≤R≤T/4 in which R is a radius of curvature of the curvedsurfaces and T is a thickness of the body in the stacking direction. 3.The multilayer capacitor of claim 1, wherein in the cover portions,corners at which the third surface is connected to the fifth surface andthe sixth surface and corners at which the fourth surface is connectedto the fifth surface and the sixth surface include curved surfaces. 4.The multilayer capacitor of claim 1, wherein 1≤δ/Wg≤1.2.
 5. Themultilayer capacitor of claim 1, wherein 0.5 μm≤Wg≤T/12.
 6. Themultilayer capacitor of claim 1, wherein 0.5 μm≤Wg≤15 μm.
 7. Themultilayer capacitor of claim 1, wherein Wg<Tg in which Tg is a marginof each of the third surface and the fourth surface.
 8. The multilayercapacitor of claim 1, wherein 10 μm≤R≤60 μm in which R is a radius ofcurvature of the curved surfaces.
 9. The multilayer capacitor of claim1, wherein the margin (δ) of each of the corners formed as the curvedsurfaces in the cover portions is smaller than a radius (R) of curvatureof the curved surfaces.
 10. The multilayer capacitor of claim 1, whereinthe plurality of internal electrodes have a uniform width.
 11. Themultilayer capacitor of claim 1, wherein in the body, when outer regionssurrounding the plurality of internal electrodes are margin regions, adensity of a dielectric layer is lower in the margin regions than inother regions of the body.
 12. A multilayer capacitor comprising: a bodyincluding a stacked structure of a plurality of dielectric layers and aplurality of internal electrodes stacked with each of the plurality ofdielectric layers interposed therebetween; and external electrodesdisposed on external surfaces of the body and electrically connected tothe plurality of internal electrodes, wherein the body includes anactive portion forming a capacitance by the plurality of internalelectrodes disposed therein and cover portions disposed on upper andlower surfaces of the active portion, respectively, in a stackingdirection of the plurality of dielectric layers, the body has a firstsurface and a second surface, to which the plurality of internalelectrodes are exposed, opposing each other, a third surface and afourth surface which oppose each other in the stacking direction, and afifth surface and a sixth surface which are connected to the first tofourth surfaces and oppose each other, in the body, corners of the coverportions include curved surfaces, a margin (δ) of each of the corners ofthe cover portions is greater than or equal to a margin (Wg) of sideportions of the body, where the margin (δ) is a distance from a surfaceof the corners of the cover portions to a closest portion of theplurality of internal electrodes, and the margin (Wg) is a distance fromthe fifth or sixth surface of the body to a closest portion of theplurality of internal electrodes, and in the body, when an outer regionsurrounding the plurality of internal electrodes is a margin region, adensity of a dielectric layer in the margin region is lower than adensity of a dielectric layer in other regions of the body.
 13. Themultilayer capacitor of claim 12, wherein in the margin region, theplurality of dielectric layers include at least two layers havingdifferent densities, and a density of a dielectric layer adjacent to theplurality of internal electrodes is higher than a density of anotherdielectric layer of the at least two layers.
 14. The multilayercapacitor of claim 12, wherein the margin region includes a plurality ofpores.
 15. The multilayer capacitor of claim 14, wherein the pluralityof pores are needle-like pores.
 16. The multilayer capacitor of claim14, wherein the plurality of pores have a form in which the plurality ofpores are aligned in a shape corresponding to an outer shape of thebody.
 17. The multilayer capacitor of claim 16, wherein the plurality ofpores are composed of a plurality of rows, where each row is defined asa row of pores that are aligned in the shape corresponding to the outershape of the body.
 18. The multilayer capacitor of claim 17, whereinpore densities of the plurality of rows are different from one another,and a pore density of a region closer to an outer surface of the body islower than densities of other regions in the plurality of rows.